A new dental cement formulation based on a mixture of zinc oxide and alumina powders and a liquid component containing ortho-ethoxybenzoic acid and hexyl vanillate has been developed for use as a dental cement. The new cement has improved mechanical and physical properties and low water solubility, as compared to more conventional zinc oxide eugenol or zinc oxide-ethxybenzoic acid cements. While the physical and mechanical properties and the microstructure have been characterized, the biological acceptance of the cement is unknown. The specific aim of this research is to evaluate the in vivo tissue reaction of the zinc oxide-hexyl vanillate cement, using two test methods. The first method consists of the well accepted in vivo connective tissue implantation test, as suggested by ADA specifications. The tissue reactions elicited by the cement will be monitored by qualitative histopathological examinations as a function of time after implantation. The second method of evaluation involves implantation of disc shaped cement specimens into the peritoneal cavity of rats. The peritoneal cavity implantation site allows for a more thorough investigation of the interaction between the observed tissue reactions and the formation of degradative products of the cement. The quantity and types of cells involved in the tissue reaction will be monitored as a function of time using the peritoneal cavity lavage technique. The tissue capsule resulting from implantation in the peritoneal cavity will be prepared for histological evaluation. The peritoneal cavity technique will therefore, combine the quantitative cellular effects and qualitative histopathological investigations of the tissue reaction to dental cements. Atomic absorption spectrophotometry and scanning electron microscopy and elemental analysis will be used in an attempt to identify degradative products of the cement which may have contributed to the foreign body tissue reaction. These biological evaluations will serve as screening procedures to describe the tissue reaction to the new dental cement and highlight the need for possible further research.